System and Method for Fingerprint Validation

ABSTRACT

The invention provides a system and method for rapid validation of identity from tissue using registered two dimensional and optical coherence tomography (OCT) scan images. The preferred embodiment provides, for a human fingerprint, validation that the surface fingerprint matches the primary fingerprint. An alternate embodiment provides validation of “aliveness” by ascertaining blood flow. Various embodiments are taught.

CROSS REFERENCES TO RELATED PATENTS OR APPLICATIONS

This application claims priority from U.S. provisional application62/013,130, docket number CI140616PR. It also relates to U.S. Pat. No.7,248,907 filed on Oct. 19, 2005 titled “Correlation of ConcurrentNon-invasively Acquired Signals”, the contents of which is incorporatedby reference as if fully set forth herein. It is also related to Pub NoUS-2014-0313515-A1, U.S. application Ser. No. 13/261,848, titled“Improved Correlation of Concurrent Non-invasively Acquired Signals” andto U.S. application Ser. No. 14/435,701 “Enhanced OCT Measurement andImaging Apparatus and Method”.

It is also related to U.S. Pat. No. 8,870,376 entitled Non InvasiveOptical Monitoring and U.S. Pat. No. 8,888,284 entitled A Filed of LightBased Device, the contents of which is incorporated by reference as iffully set forth herein. This invention is also related to U.S. Pat. No.7,526,329 titled Multiple reference non-invasive analysis system andU.S. Pat. No. 7,751,862 titled Frequency resolved imaging system, thecontents of both of which are incorporated by reference herein as iffully set forth.

GOVERNMENT FUNDING

None

FIELD OF USE

The invention relates to non-invasive imaging and analysis techniquessuch as Optical Coherence Tomography (OCT). In particular it relatesusing optical interferometric techniques to monitor or measuresub-surface attributes of human tissue in conjunction with surfaceimaging techniques. Correlation of surface images and sub-surface imagesis useful in secure identification, verification of life, authenticationof identity, and other bio-metric applications.

BACKGROUND OF THE INVENTION

Non-invasive imaging and analysis of targets is a valuable technique foracquiring information about systems or targets without undesirable sideeffects, such as damaging the target or system being analyzed. In thecase of analyzing living entities, such as human tissue, undesirableside effects of invasive analysis include the risk of infection alongwith pain and discomfort associated with the invasive process. In thecase of quality control, it enables non-destructive imaging and analysison a routine basis.

Optical coherence tomography (OCT) is a technology for non-invasiveimaging and analysis. There are more than one OCT techniques. TimeDomain OCT (TD-OCT) typically uses a broadband optical source with ashort coherence length, such as a super-luminescent diode (SLD), toprobe and analyze or image a target. Multiple Reference OCT (MRO) is aversion of TD-OCT that uses multiple reference signals. Another OCTtechnique is Fourier Domain OCT (FD-OCT).

A version of Fourier Domain OCT, called Swept Source OCT (SS-OCT),typically uses a narrow band laser optical source whose frequency (orwavelength) is swept (or varied) over a broad wavelength range. InTD-OCT systems the bandwidth of the broadband optical source determinesthe depth resolution. In SS-OCT systems the wavelength range over whichthe optical source is swept determines the depth resolution.

Another version of Fourier Domain OCT, often referred to as SpectralDomain OCT (SD-OCT), typically uses a broad band optical source and aspectrometer to separate out wavelengths and detect signals at differentwavelengths by means of a multi-segment detector.

OCT depth scans can provide useful sub-surface information including,but not limited to: sub-surface images of regions of tissue; measurementof thickness of layers of tissue; magnitude of regions of abnormaltissue growth; measurement of concentration of metabolites, such asglucose, in tissue fluids; measurement of concentration of metabolites,such as glucose, in blood. More generally OCT depth scans can provideuseful sub-surface information regarding attributes of tissue.

It is often useful to acquire OCT sub-surface scans of tissue at knownlocations with respect to the tissue surface. While OCT can produce twodimensional images of the surface of a target such as tissue, there areconventional imaging technologies that can capture surface images, suchas a camera employing a conventional charged coupled device (CCD). Suchconventional imaging devices can readily capture images of the surfaceof tissue.

Tissue can be imaged to acquire a surface fingerprint by varioustechniques including, but not limited to: cameras using one or moreconventional charged coupled device (CCD); an array of conductingsensors in conjunction with an RF generator (as in an iPhone fingerprintdetector); ultrasonic imaging systems, such as those using capacitivemicro-machined ultrasound transducers (CMUTs).

While fingerprint sensors, such as an array of conducting sensors inconjunction with an RF generator, are used to ensure use by authorizedindividuals, such sensors are vulnerable to being hacked, for example,by artificial (stick on) fingerprints. There is therefore an unmet needfor a more secure authorization technique. Moreover, while securemethods exist, they are not sufficiently fast for many consumerapplications, where the expectation is for rapid validation of identity.

Systems and method needs to be both secure and rapid to be useful. Whatis needed is a system and method for secure validation of fingerprintsthat is both rapid and capable of determining blood flow or monitoringother bio-signs as a sign of life.

SUMMARY OF THE INVENTION

The invention described herein meets at least all of the aforementionedunmet needs. The invention provides a method, apparatus and system foracquiring a sub-surface image or measurement in conjunction with asurface image of tissue at a region and compares the sub-surface imageor measurement with a corresponding surface image in order to validateaspects of the measurement or image. One aspect to be validated is thata sub-surface or sub-dermal fingerprint is compatible with thecorresponding region of a surface fingerprint. Another aspect tovalidate is that the sub-surface tissue is alive.

The preferred embodiment of a fingerprint validation system according tothe invention comprises: an optical coherence tomography system,generating one or more cross sectional tomographic scans of thefingerprint; the optical coherence tomography system and the surfaceimaging system are in a preselected physical relationship with respectto each other such that the surface image and the cross sectionaltomographic scan are registered; a processor module containing memory,electronic control and processing, surface imaging control andprocessing; the processor module—by comparing the cross sectionaltomographic scans of said fingerprint with the surface image of thefingerprint—validates that the cross sectional tomographic scan iscompatible with the corresponding region of the surface image andtransmits validation status of the fingerprint. Transmission ofvalidation status typically ensures or denies access to a device orsystem, such as, for example, an electronic device or other securedevice or system.

The preferred embodiment of the inventive method useful in validating afingerprint comprises the steps of: selecting a relative positioning ofan optical coherence tomography system and a surface imaging device,with respect to each other; performing one or more optical coherencetomography depth scans to produce a cross sectional tomographic scan ofsaid fingerprint, said scan including the interface of the epidermis andthe dermis; obtaining a surface image of said fingerprint; validating,by comparing said cross sectional tomographic scans of said fingerprintwith said surface image of said fingerprint, that said cross sectionaltomographic scan is compatible with the corresponding region of saidsurface image; outputting result of said validation step.

In an alternate embodiment, the method further includes the step ofobtaining a plurality of a cross sectional tomographic scans atsubstantially the same location, thereby enabling in less than onesecond, a determination of whether or not blood flow is present andthereby a determination of whether or not the finger is alive. In otherembodiments OCT scans are processed to monitor for other bio-signs, suchas heart rate, respiration rate or the pulsatile behavior of blood flow.

In an alternate embodiment the step of performing optical coherencetomography scan includes using multiple reference optical coherencetomography.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings provided as an aid to understanding the invention are:

FIG. 1 is an illustration of a system according to the invention.

FIG. 2 depicts an alternate embodiment of a system according theinvention.

FIG. 3 depicts a cross section tomograph (a B-scan) together with asurface image, illustrating the application of the invention to humanfingerprint verification.

FIG. 4 shows a typical B-scan showing ridges and a surface fingerprintalso showing ridges.

FIG. 5 show a surface fingerprint and the corresponding B scan.

FIG. 6 shows a 2D (two dimensional) image below the surface, and a Bscan, illustrating the absence of ridging pattern.

FIG. 7 shows a primary fingerprint, and a B-scan of the region where theepidermis and dermis meet, illustrating the matching ridges.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Terminology

A selection of terms used in this specification and the intendedmeanings are set forth hereinbelow as an aid to understanding theinvention.

-   B-scan: a cross sectional tomographic scan obtained using optical    coherence tomography; a scan that includes a sub-surface scan.-   CCD: Charge Couple Device-   CMUT: capacitive micro-machined ultrasonic transducer-   Conventional fingerprint: a surface fingerprint; an image of the    surface of the skin—the outer epidermis—on a fingertip; any    fingerprint image obtained other than by the inventive method and    system. Conventional image (and conventional imaging system)    includes an image obtained by a camera, a photocopy, or any other    common imaging techniques for imaging the surface fingerprint or    tissue layer in a two dimensional representation.-   OCT: Optical Coherence Tomography-   Primary fingerprint: a term used in the field of fingerprint    analysis, referring to the region where the epidermis and the dermis    meet. Alternately termed “sub-surface fingerprint”; “sub-dermal    fingerprint”-   Registration: the alignment of the cross sectional tomographic scan    with the conventional fingerprint. In a system according to the    invention, registration is ensured by the physical arrangement of    the optical coherence tomography system and the surface imaging    system or device. The position of the OCT is calibrated with respect    to the imaging system. Such calibration using, for example, a test    pattern, is understood by those of average skill in the relevant art    and needs no further elaboration. Calibration includes alignment at    multiple surface positions.-   Sub-surface: below the surface of the target; below tissue outermost    layer; area including tissue beneath the outermost tissue layer; The    sub-surface fingerprint, also referred to as a sub-dermal    fingerprint or as the primary fingerprint, is located at the    interface of the epidermis and the dermis. In an individual's    finger, the pattern in outermost layer of the epidermis matches the    pattern at the interface of the epidermis and the dermis. Thus, the    conventional surface fingerprint is a precise match, or, “copy” of    this sub-dermal primary fingerprint.-   Validating: determining that the target, typically a fingerprint,    matches at the surface and at the interface of the dermis and the    epidermis; validating also includes, in an alternate embodiment,    determining blood flow, hence ensuring “aliveness”. The processor    outputs validation status.-   Validation status: if positive validation, the output of status    enables secure access. If validation fails, output of validation    failure is used, for example, to decline device access.

The inventive method useful in fingerprint validation comprises thesteps of selecting a relative positioning of an optical coherencetomography system and a surface imaging device, with respect to eachother; performing an optical coherence tomography scan to produce across sectional tomographic scan of said fingerprint, said scanincluding the interface of the epidermis and the dermis; obtaining asurface image of said fingerprint; validating said cross sectionaltomographic scan using said surface image as a registration of saidfingerprint and determining whether said cross sectional tomographicscan is compatible with the corresponding region of said surface image;outputting result of said validation step.

In an alternate embodiment, the method further includes the step ofobtaining a plurality of a cross sectional tomographic scans atsubstantially the same location, thereby enabling in less than onesecond, a determination of whether or not blood flow is present.

In an alternate embodiment the step of performing optical coherencetomography scan includes using multiple reference optical coherencetomography.

Referring now to the Figures, the preferred embodiment is depicted inFIG. 1 where the target is human tissue, and specifically the regionreferred to as “fingerprint”, and where an OCT system 101 uses anoptical beam 102 to non-invasively scan the target 105. A conventionalimaging system 107 also captures a surface image of the target 105 whichis processed by a surface image control and processing module 109.

An electronic control, memory and processor module 111 processes andstores an OCT scan of the tissue, acquired by the OCT system 101 inconjunction with the conventional surface image of the target. Thephysical relationship of the OCT system 101 and the conventional imagingsystem 107 are pre-selected, and is such that the OCT scans are at knownor determined locations with respect to the conventional surface imageof the target. Because the positions of the imaging system and the OCTprobe beam with respect to each other are pre-selected so that the crosssectional tomographic scan is registered with the two dimensionalsurface image, it is possible to compare (or correlate) the structuresshown in the B-scan with the precise corresponding features of theconventional image (i.e. ridges and valleys in the dermis-epidermisinterface can be compared with ridges and valleys in the surfacefingerprint). The processing module performs the correlations, andoutputs validation that the fingerprint is a match or not.

In the preferred embodiment, the surface imaging system 107 is selectedfrom one of the following or an equivalent: a CCD imaging system with anaperture through which the OCT probe beam can be applied to the target;an imaging system that is transparent at the wavelength of the OCTsystem; an ultra-sonic imaging array such as a capacitive micro-machinedultrasonic transducer (CMUT); an OCT imaging system, which may be thesame OCT system that generates the sub-surface scans; a pressuresensitive array, such as is described in U.S. Pat. No. 7,795,062 titled“Method of forming a pressure switch thin film device”.

FIG. 2 depicts an alternate embodiment. It is in many respects similarto FIG. 1, however, the surface imaging device 207 is offset from thepath of the OCT probe beam. It can be appreciated that such an offset isnecessary if the surface imaging device is not transparent. In analternate embodiment, the surface imaging probe beam 209 is selectedfrom a group of probe beam types, including an RF probe beam or anultrasound probe beam.

FIG. 3 depicts a conventional surface fingerprint 301 of a typical humanfinger 303 and an OCT B-scan 305 of a region of the finger taken at aknown location with respect to the surface image, indicated by theregion between the two arrowheads inside the small oval. An enlargedview 307 more clearly depicts the small oval and the arrowheads thatdefine the region of the OCT B-scan 305.

In FIG. 4 the OCT B-scan 401 and the enlarged view 402 of the surfaceimage are more clearly depicted. The arrows 403 and 405 indicate theregion that corresponds to the cross sectional tomograph commonlyreferred to as an OCT B-scan 401. The OCT B-scan 401 includes adepiction 407 of the surface fingerprint image and also includes adepiction of a sub-surface version of the fingerprint 409, oftenreferred to as a primary fingerprint. The sub-surface or primaryfingerprint is generally understood to be the region where the epidermisand dermis meet.

The electronic control, memory and processor module 111 (of FIGS. 1 and2) compares the sub-surface fingerprint image 409 with the portion ofthe B scan showing the surface [OCT image 407] and with the conventionalfingerprint image 402 to validate that the sub-surface fingerprint iscompatible with the corresponding region of a surface fingerprint.

In the preferred embodiment, validation confirms that that thesub-surface (or primary) fingerprint 409 has contours that correspond tothe contours of the surface fingerprint, i.e. that the sub-surface imageand the surface image are appropriately compatible. For example the darkline 411 of the enlarged view of the surface image 402 corresponds tothe OCT surface detail to the right of 413 and the deeper sub-surface(or primary) image farther to the right of 413 (along the contour of409). The processing module outputs validation status. Validationstatus, for example, enables or prevents unlocking of a coupledelectronic device such as, for example, a smart phone, a home securitysystem, and other devices where secure access is desired. Note, thesurface fingerprint image 402 is a typical example of and image and usedherein for illustrative purposes.

While the preferred embodiment describes an OCT B-scan 401 of FIG. 4taken along a substantially straight line (between the arrow heads of403 and 405 of FIG. 4) of a corresponding conventional fingerprintimaging device many variations of the invention are possible. The OCTscan need not be a straight line. In an alternate embodiment, the OCTscan consists of an irregular line that is scanned with either a randomor a particular relationship to features of the surface fingerprint.

In an alternate embodiment, the OCT performs a lateral scan consistingof a two dimensional scan, such as a raster scan, providing a volumetricimage. Such a volumetric image is compared to a surface image taken witha surface imaging device including, but not limited to, a CCD camera, anultra sound imager, an RF imager, an array of pressure switches.Alternatively such a volumetric image is used to generate the surfaceimage, thus removing the requirement for a separate surface imager.

FIG. 5 illustrates a 2D image of a surface fingerprint 501 volumetricdata generated by an OCT scanning system. FIG. 5 also depicts an OCTB-scan 502 which is a two dimensional depth image of the region of the2D tissue image 501 indicated by the dashed line 503. The depicted 2Dimage of a surface fingerprint 501 is generated from OCT data just belowthe surface of a glass interface against which the finger was pressedand is indicated in the B-scan 502 as the dashed line 504. The dashedoval 505 surrounds a distinctive feature of the surface fingerprint.

FIG. 6 illustrates a 2D image of a surface region 601 at a depthindicated by the dashed line 602 of the B-scan 603. This surface region601 is at a depth beneath the surface fingerprint and above theepidermis dermis interface. The B-scan 603 is again located at theregion indicated by the dashed line 604 of the 2D image 601. There is nosimilarity between this 2D image and the surface fingerprint image 501of FIG. 5.

FIG. 7 illustrates a 2D image of a surface region 701 at a depthindicated by the dashed line 702 of the B-scan 703. This surface region601 is at a depth in the region of the epidermis dermis interface. TheB-scan 703 is again located at the region indicated by the dashed line704 of the 2D image 701. This primary (sub-surface or sub-dermal) 2Dfingerprint image 701 has a high degree of similarity with surfacefingerprint image 501 of FIG. 5.

The similarity between the primary or sub-dermal 2D fingerprint imageand the surface fingerprint image 501 of FIG. 5 is clearly evident inthe regions depicted within the ovals 705 of FIG. 7 and 505 of FIG. 5.This high degree of similarity between the surface and sub-surfacefingerprint images of an actual finger enables using conventional imageprocessing techniques to measure the degree of correlation between twosuch images and to determine whether or not the images (and hence thesurface and sub-surface fingerprints) correlate, i.e. to validate thatthe images are compatible with being different images of the samefinger.

In the preferred embodiment aspects of the primary fingerprint at theepidermis dermis interface of one or more B-scans are compared with thecorresponding regions od the surface fingerprint. In an alternateembodiment where a large number of adjacent B-scans, constituting avolumetric scan, are available, a 2D sub-surface primary fingerprint canbe compared with the 2D surface fingerprint.

The surface and sub-surface fingerprint 2D images of an actual fingercan be compared using conventional image processing techniques tomeasure the degree of correlation between two such images and todetermine whether or not the images (and hence the surface andsub-surface fingerprints) correlate. Alternately the images can beprocessed to analyze for fingerprint minutia (as is well known to thoseskilled in the art of processing fingerprints) and then the minutia ofthe two images can be compared.

In an alternate embodiment the OCT system is the only imaging system andin an enrollment process an extensive volumetric scan of the fingerprintis acquired and stored. In subsequent validation a small set of B-scans,such as the eight B-scans depicted by the eight white lines of FIG. 4 isacquired and compared to the stored volumetric scan. If a matching setof corresponding B-scans are found in the stored volumetric scan thenthe fingerprint is validated.

It can also be appreciated that in another alternate embodiment, arandom (or quasi-random) group of point scans are registered by means ofthe surface fingerprint and compared with extensive previously takenreference OCT data to validate correct tissue layer thickness atparticular points. A further alternate embodiment provides an OCT systemwith multiple optical probe beams to acquire multiple OCT scanssimultaneously.

In a system according to the invention, the OCT is selected from thegroup of any version of either Time Domain-OCT or Fourier Domain OCTsystems, including the multiple reference version of Time Domain-OCT(described in some of the references incorporated herein).

In an alternate embodiment, successive OCT B-scans can be taken atsubstantially the same location and correlated to check for the presenceof blood-flow to validate that the tissue being analyzed is alive (andnot, for example a fake or non-living finger). The location of othertissue features, such as sweat glands could be monitored as additionalidentification fiducial markers.

In an alternate embodiment, one or more sweat glands are repeatedlyscanned to monitor for changes in the scattering characteristics of suchsweat glands. Changes in the scattering characteristics of sweat glandscan be processed to determine stress levels of the individual beingscanned.

A correlation mapping method using OCT to detect blood flow, and hencealiveness is described in the paper titled “Correlation mapping methodfor generating microcirculation morphology from optical coherencetomography (OCT) intensity images,” by authors Jonathan E, Enfield J,Leahy M J., published in J. Biophotonics, 4(9), 583-587 (2011). Thispaper is incorporated herein by reference.

While the preferred embodiment is described with respect to afingerprint, any identifying fiducial, such as a freckle or a skinblemish, could be used to validate a sub-surface image or measurementwith a surface image.

Moreover, while the preferred embodiment is described in terms of asecurity application, the invention could also be used for safety. Forexample, only when an appropriate surface fingerprint or fiducial isrecognized from the surface imager, is the OCT optical probe signalenabled at high power. This could ensure the device could not emit highpower when, for example, it could be directed into an individual's eye.

As another safety example, if the device were making a bio-measurement,such as a glucose concentration measurement, that would determine amedical treatment, such as the provision of insulin, then validatingthat the identity of individual being measured would be a useful safetyprecaution.

Many variations of the above embodiments are possible. The scope of thisinvention should be determined with reference to the description and thedrawings along with the full scope of equivalents as applied thereto.

11. A method of validating a fingerprint, said method comprising thesteps of: selecting a relative positioning of an optical coherencetomography system and a surface imaging device, with respect to eachother; performing an optical coherence tomography scan to produce across sectional tomographic scan of said fingerprint, said scanincluding the interface of the epidermis and the dermis; obtaining asurface image of said fingerprint; validating said cross sectionaltomographic scan using said surface image as a registration of saidfingerprint and determining whether said cross sectional tomographicscan is compatible with the corresponding region of said surface image,and determining blood flow, hence ensuring liveness of said target;outputting result of said validation step, where if positive validation,the output of status enables secure access.
 12. The method of claim 11wherein the method further includes the step of obtaining a plurality ofa cross sectional tomographic scans at substantially the same location,thereby enabling in less than one second, a determination of whether ornot blood flow is present.
 13. The method of claim 11 wherein successiveOCT B-scans are taken at substantially the same location and correlatedto check for the presence of blood-flow to validate that the tissuebeing analyzed is alive.